This invention relates generally to golf clubs and, in particular, to so-called metal wood-type golf clubs.
Golf clubs known as xe2x80x9cwoodsxe2x80x9d traditionally have a head made of a suitable wooden material such as maple or persimmon attached to one end of an elongated shaft. These wooden club heads are usually solid and are shaped with their weight properly distributed about their center of gravity to maximize performance. Golf club xe2x80x9cwoodxe2x80x9d heads have also been formed of suitable metals such as stainless steel and titanium. Metal heads are usually hollow. Various attempts have been made to distribute weight in metal heads with respect to their center of gravity so that the performance is maximized. Such attempts have included placing different types and numbers of weight members at different locations inside the metal heads. Examples of such attempts are disclosed in prior U.S. Pat. No. 4,869,507 to Sahm; U.S. Pat. No. 5,058,895 to Igarashi; U.S. Pat. No. 5,141,230 to Antonious; and, U.S. Pat. No. 5,219,408 to Sun.
The Sahm patent teaches that lowering the center of gravity of a club head would tend to add more loft to a golf shot. Igarashi teaches that perimeter weighting increases the moment of inertia of a wood type club. The increased moment of inertia causes the club to resist twisting when a ball is not struck at the xe2x80x9csweet spotxe2x80x9d, that is, the point on the club face at which a line normal to the face passes through the club head""s center of gravity. Reducing the twisting causes the ball to travel with less loss of directional control. None of the aforementioned prior art patents, however, teach use of a weight member to tailor gear effect-induced topspin to partially offset the natural loft angle induced backspin of a metal wood-type club.
The present invention comprises a metal wood-type golf club comprising a hollow body with a face disposed at a predetermined loft angle adapted for impacting a golf ball. In a preferred embodiment of a golf club, a weight member is disposed along the interior surface of the bottom wall. The weight member is sized and distributed so as to increase the moment of inertia of the golf club about a vertical axis extending through the center of gravity as well as lowering the center of gravity of the club head itself. Additionally, the longitudinal position of the weight member is selected as a function of the loft angle of the club face so that the gear effect about the center of gravity partially offsets the natural backspin of the club. The weight pad is moved forward for a club having a small loft angle and moved rearward for a club having a high loft angle.
Moving the center of gravity fore and aft as a function of loft angle permits clubs to be designed to take advantage of vertical gear effect to tailor the amount of backspin imparted to a golf ball for a given loft angle, thereby enabling the club to deliver the ideal trajectory without over spinning or under spinning the ball.